Note: Descriptions are shown in the official language in which they were submitted.
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Use of a regenerated cellulose fibre
The present invention relates to the use of a regenerated cellulose fibre,
which is obtained by
the viscose process, in flame-retardant products.
Flame-retardant viscose fibres have many fields of application, such as, e.g.,
safety clothing,
mattress fillings, textiles for interior use, etc., intending to provide
general safety and
protection.
There have been known already different types of flame-retardant viscose
fibres:
On the one side, it is known to provide viscose fibres with flame-retardancy
by integration of
polysilicic acid. The integration of polysilicic acid, however, leads to the
formation of rigid,
brittle fibres, which are suitable for fleece textiles rather than for textile
uses.
Under the trade name Lenzing FR there are marketed viscose fibres, which are
obtained by
the integration of a phosphorus-containing additive. In order to obtain a
sufficient flame-
retardancy with phosphorus-containing additives, there has to be accomplished
a high level
of integration. This will lead, due to the high costs of additives, to a
rather high final price of
the fibre.
There is existent a variety of proposals for subsequently conferring flame-
retardancy to
cellulose fibres, this is, application onto the already fabricated fibres,
such as, e.g., Probane
(THPC) and Pyrovatex CP.
Textiles / fibres that are post-treated in such a way, however, only have a
limited resistance
to washing. Due to the cross-linking chemistry used, there are developed
residual amounts of
formaldehyde, which presents a health risk. Furthermore, the cross-linking
reaction causes
an embrittlement and stiffening of the fibres / textiles.
The US 3 734 683 describes the flame-retardant effect of the cellulosic fibres
with a higher
portion of carboxy groups due to the production of a carboxycellulose.
According to this
publication, viscose fibres are oxidized in a complex method and subsequently
post-treated.
In an economically sound process for the production of fibres, this method
cannot be carried
out. The mentioned oxidation would, furthermore, lead to damage to the fibre
structure and a
flawed processability.
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The object of the present invention is to provide a cost-efficient and
effective flame-retardant
fibre, which is easy to process in the conventional textile processes.
This aim is solved by the use of a regenerated cellulose fibre, in which
carboxymethylcellulose is incorporated, in a flame-retardant product.
Preferred embodiments are listed in the sub-claims.
DETAILED DESCRIPTION OF THE INVENTION
It has surprisingly been shown that a regenerated cellulose fibre, which has
incorporated
carboxymethylcellulose (CMC), acts as a flame-retardant and may be processed
in a
comparably cheap as well as good way.
Under the measure that there is incorporated carboxymethylcellulose into the
fibre the expert
understands that the CMC isintegrated in the matrix of the (upon regeneration
of the fibre)
underivatised cellulose. This is - in contrast to the application of CMC onto
the already
fabricated fibre - possible, among other, by spinning in CMC into the viscose
dope.
Viscose fibres with a portion of carboxymethylcellulose (CMC) have been known.
This is a
mixed fibre, which is obtained by spinning in carboxymethylcellulose into the
viscose dope.
Such fibres were also produced on a commercial level (US 4,199,367 A, US
4,289,824 A).
There is produced, for example, a viscose dope according to the conventional
methods.
There are added to the dope, directly before the spinning out, 8-12 % by
weight solution of
carboxymethylcellulose (CMC) so that this leads to the desired integration
amount based on
underivatised cellulose. Post-treatment and drying are carried out according
to the
conventional methods.
The portion of incorporated carboxymethylcellulose in the regenerated
cellulose fibre is
preferably 5 % by weight to 50 % by weight, especially preferably 15 % by
weight to 40 %
by weight, most preferably 20 % by weight to 30 % by weight, based on
underivatised
cellulose.
The carboxymethylcellulose may be a commercially available product with a
degree of
substitution of 0.6 - 12, preferably 0.65 - 0.85 and a viscosity (2% solution;
25 C) of 30-800
mPas; preferably 50-100 mPas.
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The CMC containing regenerated cellulose fibre used according to the invention
is also
designated as õviscose-CMC mixed fibre" in the following.
The fibre titre of the viscose-CMC mixed fibre is preferably from 0.5 dtex to
8 dtex,
especially preferably from 1.3 to 6 dtex.
The fibre length of the viscose-CMC mixed fibre used according to the
invention may be 2
mm to 80 mm and is in particular dependent on the field of application. For a
wet-laid
process, there are suitable fibre lengths of 2 to 20 mm, for a carding
process, there are
suitable fibre lengths of 20 to 80 mm.
The viscose-CMC mixed fibre contains preferably another flame-retardant
additive. This
further additive may be in particular selected from the group consisting of
halogen
containing additives, phosphorus containing additives, aluminium and magnesium
salts and
polysilicic acids. The further additive may be incorporated in the fibre in
the known method
of spinning into the viscose dope (e.g., in the case of phosphorus-containing
additives such
as, e.g., Exolit 5060) or being subsequently applied onto the fibre (e.g., in
the case of
alkaline solutions of an aluminium salt).
The viscose-CMC mixed fibre used according to the invention or textiles or
fleece cloths that
contain these, respectively, discontinue to burn in contrast to viscose fibres
or products made
from pure viscose fibres following ignition. The flame extinguishes
immediately, and the
fibre merely continues to smoulder. Especially pronounced is this effect in
association with
an integration of 20 % by weight CMC based on underivatised cellulose.
The viscose-CMC mixed fibres used according to the invention, however, differ -
in contrast
to some of the already known flame-retardant viscose fibres - in their values
of tenacity and
elongation values as well as their elasticity not substantially from
conventional viscose fibres
and thus may be processed in the same way as these.
The additive (CMC) used for the fibres according to the invention does not
present a health
risk and is even used as foodstuff additive. Embrittlement and stiffening of
the fibres does
not occur. The flame-retardant effect is resistant to washing in a nearly
unlimited way.
Accordingly, the present invention also relates to a flame-retardant product,
containing a
regenerated cellulose fibre, in which carboxymethylcellulose is incorporated.
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The flame-retardant product according to the invention is preferably
characterized in that the
portion of incorporated carboxymethylcellulose in the cellulose fibre is 5 %
by weight to 50
% by weight, preferably 15 % by weight to 40 % by weight, especially
preferably 20 % by
weight to 30 % by weight based on underivatised cellulose.
The flame-retardant product according to the invention may contain preferably
the viscose-
CMC mixed fibre in a portion of 10% - 100%.
The flame-retardant product according to the invention is preferably selected
from the group
consisting of clothing, in particular safety clothing, home textiles, in
particular mattresses,
automobile textiles, filter materials and insulation materials for the
construction and
automobile field.
EXAMPLES:
There were produced in a well-known process viscose - CMC mixed fibres with a
portion of
0% (zero samples), 12% by weight, 20 % by weight and 30 % by weight CMC based
on
underivatised cellulose. The fibres were cut to a staple length of 40 mm.
From the fibre samples there were produced rotor rings each having 10 g. The
rotor rings
were subsequently opened and pressed by a tampon calandar. The produced bands
have a
weight per unit area of about 238g/m2 (206 - 260 g/m2) with a thickness of
about 5mm.
For the fire tests there were cut test samples with a size of 8 x 2 cm. The
test samples were
horizontally or vertically clamped, and the free end of the sample was fired
over a defined
period of time with a Bunsen burner.
Results:
Conventional viscose fibre (0% CMC):
The samples ignited already at 1 s firing time and subsequently continued to
burn with a
dynamic pattern until complete combustion.
Viscose fibres with 12% or 20%, respectively, CMC (according to the
invention):
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The test sample incinerates upon direct contact with the burner flame. If the
flame is
removed, the sample, however, will immediately extinguish ("self-
extinguishing"). In some
cases several individual fibres that projected beyond the test sample
continued to burn upon
removal of the flame.
The flaming time was varied from 1 s - 10 s. All samples extinguished directly
upon
removal of the flame. There was increased only the burnt portion due to longer
contact with
the burner flame.
All samples still smouldered upon extinction. In all cases, there was
developed a slow and
complete ashing of the test samples.
